hecker



Jan. 31, 1956 H. K. HECKER LIFTING DEVICES I5 Sheets-$heet 1 Filed March 11, 1949 INVENTOR Harvard K. Hack- ATTZRNE'Y Jan. 31, 1956 H. K. HECKER 2,732,917

LIFTING DEVICES I5 Sheets-Sheet 2 Filed March 11, 1949 INVENTOR Harvard K. Hacker Ian. 31, 1956 H. K. HECKER 2,732,917

LIFTING DEVICES Filed March 11. 1949 3 Sheets-Sheet 3 INVENTO R Harvard KY Hecker' BY ATTORAEY dsteta Paten LIFTINGYDEVICES Application March 11, 1949, Serial No. 80,869

Claims. (Cl. ISL-8.62)

This invention relates to improvements in lifting devices. More particularly, this invention relates to improvements in lifting devices that can be used to elevate automotive vehicles.

It is therefore an object of the present invention to provide an improved lifting device that can be used to elevate automotive vehicles.

In the construction and installation of lifting devices for automotive vehicles, it is sometimes desirable to locate the lifting devices in pits or recesses below the floorsof the structures in which the lifting devices are to be operated. Hinged cover plates or doors are customarily provided to close the open upper ends of such pits or recesses; and it is desirable that those cover plates be open whenever the lifting devices move into or out of the pits or recesses, but be closed at all other times. The present invention provides a door-operating mechanism for lifting devices that positively moves the doors to open position whenever the lifting devices enter or emerge from the pits or recesses,,

but that permits the doors to move individually to closed position under the pull of gravity at all other times.

The door-operating mechanism provided by the present invention includes a number of movable levers and cams, but allof those elements are secured to and supported by an integrated supporting frame. This frame is made as, a-

simple, compact unit which can be installed with ease; and it has a plate which can be secured to the cylinder of the lifting device to precisely align the operating mechanism with the rest of the device.

Where eccentric chocks are used, and where those chocks are tall, the problem of adjusting those chocks on a transverse support is not easy; particularly, since the cover plates or doors for the lifting device will be open at the time the chocks are to be moved into register with the vehicle. The present invention furnishes aIsatisfactory solution to the problem by providing slots in the doors for the lifting device that are large enough to permit an actuator to be passed through them and into engagement with the lower portions of the chocks. It is desirable to hold the transverse support and its chocks in register with the pit or recess until the chocks engage the under portions of the vehicle to be elevated, and it is also desirable to hold that bar and those chocks in register with the pit or recess as they enter that pit or recess. Prior lifting devices have used elongated plungers that are coextensive with the lifting plungers and are held against rotation by cylinders embedded below the recess or pit; but those elongated plungers obstruct the working areas, and they are expensive. It is therefore. an object of the present invention to provide a lifting device with a cam that holds the transverse support and its chocks in alignment with the recess or pit whenever the transverse support enters or leaves the recess or pit but frees that support at all other times.

Other and further objects and advantagesof the present invention should become apparent from an'examination of the drawing and accompanying description. In the drawing audaccompanying description two preferred embodiments of the present invention have been shown and described but it is to be understood that the drawing and accompanying description are for the pur-,

poses of illustration only and do not limit the invention and that the invention will be defined by the appended claims. 7

In the drawing, Fig. 1 is a broken-away, partially-sectioned, front view of a pit which receives the supporting structure of a lifting device and which has doors and a door-operating mechanism, and this view is taken along the plane indicated by the line 1-1 of Fig. 5,

Fig. 2 is a broken-away, partially-sectioned end view of the pit of Fig. 1, it is taken along the planes indicated by the line 22 of Fig. 5, and it shows the doors in closed position,

Fig. 3 is a broken-away, partially-sectioned end view of the pit of Fig. 1, his taken along the plane indicated by the line 2--2 of Fig. 5, and it shows the doors in open position,

Fig. 4 is a partial, side elevational view of the upper end of the pit of Fig. 1, and it shows the doors open and one of the vehicle-engaging chocks extending upwardly from the pit,

Fig. 5 is a plan view of the pit of Fig. 1 with the doors closed,

Fig. 6 is an end view of a modified form of transverse support usable with the lifting device provided by the present invention, and

Fig. 7 is a plan view of the transverse support of Fig. 6.

Referring to the drawing in detail, the numeral 10 denotes a pair of angles which cooperate with two angles 12 to form a generally rectangular border. The angles 10 and .12 can be secured together by suitable means. This border supports a thin, sheet metal casing 16 which is of generally rectangular form and has the sides thereof de? pending downwardly from the vertical faces of angles 10 and 12. The casing 16 is open at the bottom, but it has a short portion at the bottom of each side thereof bent inwardly to form a flange. The flanges at the bottoms of the four sides are joined together, as by welding, and greatly strengthen the casing 16.

A reinforcing angle 14 is secured to the rear of each of the angles 12, as by welding; and the angles 14 serve to reinforce the border while also serving as an anchor to maintain that border in position when the border and casing are surrounded by supporting material. This anchor ing action largely enables the structure provided by the present invention to support the weight of an automotive vehicle driven upon or over that structure. A reinforcing angle 18 is secured to each of the long walls of casing 16.

The border and its depending casing are used to define a pit or recess adjacent the upper end of the cylinder 22 of a lifting device; and the cylinder 22 will be embedded below the floor of the garage or service station. The cylinder 22 will be connected to a source of hydraulic fluid, not shown; and it has a packing gland 24 at the top thereof. The gland 24 is held in position by a number of cap screws 32, one of which is shown inthe drawing. The cap screw 32, that is shown in the drawing, maintains a flange 28 aligned and in assembled relation with the gland 24 and cylinder 22; and that flange is permanently attached to or made a part of a hollow form 26. The form 26 is a hollow parallelepiped of rectangular cross section, and it will be secured to the gland 24 of cylinder 22 prior to the time the supporting material is placed around the upper end of cylinder 22.

The cap screw,32 shown. in the drawing also maintains an angle 30 in assembled relation with the cylinder 22; and this angle is secured at each of its ends to ver tically disposed L-shaped supports 34 and 36 by screws 40. The Lshaped supports 34 and 36 are preferably formed by cutting'ninety degree sections from the vertical grees at those points; The supports 34 and 36 extend vertically upwardly from the-ends of angle 30, and they have their horizontally disposed bent portions extending outwardly toward the walls of the pit. That portion of the vertical surface of angle 30 Which'is'between the L- shaped supports 34 and 3'6'is out completely away, and that portion of the horizontal surface of angle 30 which is between the L-shaped' supports 34 and 36 is cut away to the line 31; thus the angle 30 provides a space betweenthe L-shaped supports 34 and 36 while maintaining those supports in assembled relation. A supporting pad 38 is welded or otherwise secured to the lower ends of both of the L-shaped supports 34 and 36; and that portion of the pad 38 which extends between the supports 34 and 36 is. cut away to the line 39. Consequently, the pad 38' also provides a space between the supports 34 and 36 while maintaining those supports in assembled relation. The space provided by the pad 38 is in register with the space provided by the angle 30, and the combined space is slightly larger than and is in register with the upper end of the form 26; and the form 26 will be disposed between the L -shaped. supports 34 and 36.

The L-shaped supports 34 and 36 extend vertically upward from the pad 38, which rests on the floor f the pit and'bears the weight applied to the supports 34 and 36 by vehicles driven over or upon the structure provided by the present invention, and the horizontal portions of the supports 34 and 36 extend toward and underlie the angles 12 of the border. The ends of the horizontal portions of supports 34 and 36 are secured to angles 12 by flush type screws, not shown, which extend downwardly through openings in the angles 12 and seat in the ends of the supports 34' and 36. The securement of the lower ends of the L-shaped supports 34 and 36 to the gland 24 of cylinder 22, through the medium of angle 30, and the securement of the upper ends of the supports 34 and 36 to the angles 12 coact to hold the supports 34 and 36 rigid.

A second set of L-shaped supports 34 and 36 is provided in the pit; and this second set is placed on that side of cylinder 22 which is opposite to the first set of L-shaped supports. The second set of L.-shap'ed supports 34 and 36 are secured together by an angle and pad which are similar to angle and pad 38 but which are not cut away. The second set of L-shaped supports 34 and 36 rest on their pad, and they extend upwardly for securement to the angles 12.

The transversely-extending angles 12 support a number of cover plates or doors that arev openable to permit the vehicle-supporting structure of the. lifting device to enter and emerge from the pit. One pair of doors is located adjacent one end of the pit, and those doors are denoted by the numeral 44. Pivot pins 49 are carried by those doors, and those pins are held by pivot blocks 46. Those blocks underlie and are secured to the horizontal surfaces of angles 12, and they also underlie and are secured to narrow plates 47 which extend between the inner edges of angles 12 and the outer edges of doors 44'. The plates 47 are rigidly secured to the angles 12, as. by being welded to angles 48. that underlie and are welded to angles 12.

Another set of doors is located adjacent the center of the pit, and those doors are denoted by the numeral 50. Pivot pins 53 are secured to'the doors 50, and those pins are held in pivot blocks 52. The blocks 52 underlie and are secured to the horizontal surfaces of angles 12. The doors 50 are wider than the doors 44' and their outer edges are located immediately adjacent the inner edges of the angles 12. The doors 50 are directly in register with the cylinder 22 and they extend laterally only a short distance beyond the sides. of that cylinder.

The remaining doors are adjacent. the other end. of the.

pit, and those doors are denoted by the numeral 54. Rivot P 5 scc lted to the doors 54 and those pins are held by pivot blocks 56. The blocks 56 underlie and are secured to the horizontal portions of angles 12 and underlie and are secured to plates 47. The doors 54 are identical to the doors 44 except for cam plates v'hich are secured to the under faces of the doors 44 and 54. The cam plates 62 on the doors 44 are adjacent those ends of the doors which are closest to doors and the cam platesv 62. on the doors 54 are adjacent those ends of the doors which are closest to the doors 50. Two efthe, four doors 44 and 54. are provided with an elongated slot 60; the slots 60 being spaced rather closely to the pivot pins carried by those doors.

The four cam plates. 62 on the under. surfaces of doors 44 and 54 are selectively engaged by pins 64 which are carried on four eccentric arms 66. Two of those eccentric arms are fixedly secured to an elongated shaft 68; and they are set in register with each other so that when one of the pins 64 moves a door 44, another pin 64 will move door 54 an equal amount. The other two eccentric arms 66 are fixedly secured to a second. elongated shaft 68' which is disposed behind shaft 68 in Fig. 1. The two eccentric arms which are secured to the second shaft 68 are also in register with each. other, and they will cause conjoint movement of a door 44 and a door 54. The two shafts 68 are rotatably supported. at their ends by depending brackets which are secured to the undersurfaces of the horizontal portions of the L-shaped supports 34 and 36 by a bolt and nut 69 and 71. Shims 73 are provided between the brackets 70 and the under surfaces of the supports 34 and 36, and those shims can be adjusted to determine the normal setting of the pins 64 and thus the doors 44 and 54. The brackets 70 support spacing bars 72 which extend between and are welded to the brackets 70. Thus the brackets 70 and spacing bars 72 form integrated units. A crank arm 74 is fixedly secured to each of the shafts 68, and movement of those arms causes the eccentric arms 66 to move. The crank arms 74 have connecting rods 76 pivoted to them, andtheconnecting rods 76 are pivoted to cams 78. Each of the cams 78 has an obtuse angle intermediate its ends, and the apex of that angle constitutes the bearing face of the cam. The two cams 78 are rotatable about pivots 80 which are mounted in the vertical portions of the first set of L-shaped supports 34 and 36. Cotter keys 82 are passed through openings in both ends of the pivots 80 to maintain the pivots 80 and the cams 78 in assembled relation with the L-shaped supports 34 and 36. Springs 84 extend from openings 85 in the horizontal portions of the L-shaped supports 34 and 36 to the pivots between connecting rods 76 and cams 78. With this arrangement, the springs 84 tend to rotate the cams 78 so their bearing surfaces project into the space between the adjacent faces of L-shaped supports 34 and 36; but rotation of the cams 78 will be limited by the engagement of connecting rods with shafts 68.

The engagement of connecting rods 76 and cams 78 will hold the confronting faces of cams 78 centered between the supports 34 and 36'. The cams 78 are so positioned that they underlie the doors 50, and they will thus be accessible whenever those doors are open even though the doors 44 and 54 are close. Whenever the bearing surfaces of the cams 78 are not held apart by actuator 86 on a transverse support 88, the connecting rods 76 will hold the shafts 68 in such positions that the eccentric arms 66 and their pins 64 will be out of contact with the cam plates 62. At such times, the doors 44 and 54 will respond to the action of gravity and move to closed po sition. In that position the doors 44 and 54 rest upon the horizontal portions of L-shaped supports 34 and 36; and the supports 34 and 36 will support those doors strongly enough to permit automotive vehicles to be driven over those doors.

The two sets of L-shapedsupports 34 and 36, the an les.

- 30, the pads. 38, the. brackets 70, the spacing bars 72,

that; and 1 4, and the angles 10 constitute. an integrated framethat supports casing 16. i This frame can be fully assembled with the doors and door-operating mechanism prior to shipment and the entire structure can be installed as a unit; and in installing the structure, the angles 30 are placed in register with the proper threaded openings in gland 24 on cylinder 22, cap screws 32 are passed throughthose angles and set in those openings, and then screws are passedthrough openings in angles 12 and set in the upperends ofsupports 34 and 36.-

In removing the supports 34 and 36, the screws that normally hold those supports to angles 12 are removed, the brackets 70 are removed, cotter keys 82 and pivots 80 are removed, screws 32 are removed, andthe brackets are skewed and lifted fromthe recess or pit. The confronting bearing surfaces of cams 78 are normally held adjacent each other by springs 84, but theyare movable out of engagement with each other by the action of the actuator 86 on transverse support 88. That support is secured toga plate 90 which can be mounted on the top of a plunger 92 which reciprocates within cylinder 22. Upward movement of the support 88 will cause the upper'edges of chocks 94 to engage and open the doors 44 and 54. As the transverse support 88 continues to move upwardly, the doors 44 and 54 will open sufliciently to permit the long upper surfaces of chocks 94 to pass, and then the doors 44 and 54 will move inwardly against the tapering sides of those chocks. The free edges of the doors 44 and 54 will continue to follow the sides of chocks 94 until the cams 62 engage the pins 64, which pins will have been moved to dooropening position by the engagement of transverse sup port 88 with earns 78. The support 88 will move the cams 78 apart, thus pulling, connecting rods 76 downwardly and rotating eccentric arms 66, with their pins 64, to door-opening position. Thereafter the support 88 will engage and open the doors .50; and those doors will be opened even further by the plate 90 and plunger 92, and they will be held open by resting against the sides of plunger'92. Continued upward movement of support 88 will move that support out of engagement with cams 78; but at such time, the actuator 86 will be interposed between earns 78 andwillkeep the cams 78 apart. As the support 88 moves still further upward, the/bearing surfaces of cams 78 will follow the tapered lower end of actuator 86, and at such time the pins 64 will be moved out of engagement with cam plates 62 by the action of springs 84 on connecting rods 76. The doors 44 and 54 will then be permitted to close. However, if it is ever desirable to open the doors 44 or 54, it is only necessary to grasp those doors androtate themto open position since they can be moved individually and are not positively linked to the door-operating mechanism.

When the transverse support moves downwardly, the

lower end of actuator 86 will pass through the opening bounded by the spaced-apart confronting edges of the doors 50, which are held open by the plunger 92, and will engage the bearing surfaces of earns 78, thereby forcing them apart. That action causes rotation of shafts 68 and opens the doors 44 and 54. Those doors will be opened still further by'the inclined sides of chocks 94; and only after the chocks are within the recess will the doors 44 and 54 close. The doors 50 will close as soon as support 88 is within the recess.

- The actuator 86 performs additional functions in that it holds the transverse support 88 in alignment with the re cess or pit, as that support'moves upwardly with plunger 92, until after the chocks 44 on that supportengage the automotive vehicle; and it also shiftsthat support into alignment with the recess, if that support is slightly out of alignment with that recess, as 1 that support moves downwardly with the plunger 92. The engagement between the vertical portions of the L -shaped supports 34 and 36 and the sides and bottonrIof actuator 86 provide this aligning action. A major realignment of the supp rt 88 with the recess o pit is not required because; that support is held substantially in alignment with that recess or pit by the actuator 86 until after that support has .en-

gaged the under frame of the vehicle during the upward movement of the plunger 92; and thereafter that engagement between the support'88 and the under frame of the vehicle will keep that support substantially aligned. I However, the vehicle can sometimes shift slightly as the two posts of the lift raise it upwardly, and it can thus cause minor misalignment of the support 88. Any such misalignment will be corrected by the interaction of the actuator 88 and the vertical portions of the L-shaped supports 34 and 36.

The chocks 94 are slidably mounted on the transverse support 88, they extend upwardly at an angle to the axis of that support, and the vehicle engaging portion of each of those chocks is about three times as long as the support is wide. Because of the inclination of those chocks to the axis of thesupport 88, those chocks will tilt and clamp themselves in position on that support when they engage and support an automotive vehicle.

Stops 98. are provided on the outer ends of the support 88 to prevent separation of the chocks 94 from that support, and also tokeep those chocks from moving-so far outwardly that they will not fit within the pit when the plunger 92 is lowered. Stops 99 are provided adjacent the center of the support 88 to keep those chocks from striking the supports 34 and 36.

Openings 96 are provided in-the vertical portions of the chocks 94, and those openings can be placed in register with the slots 60 in the doors 44 and 54 when those doors are opened. This arrangement is illustrated in Fig. 4, and it enables arod-like poker 100 to be passed through the slots 60 in the doors 44 and 54 and extended into the openings 96 in the chocks 94. This poker can be used to apply transverse forces to the chocks 94, and since the openings 96 are close to the base of the chocks 94, those forces will not cause tilting and binding of the chocks. r i

The poker 100 has a right angle bend adjacent one end thereof and a bend of lesser degree adjacent the other end thereof. The rightangle bend is useful in facilitating the shifting of exposed chocks, as for example chocks that might be. used on the supporting structure at the rear end of the vehicle; and the bent portion can be used to push or pull those chocks to the desired position. The bend of lesser degree is useful in facilitating the shifting of chock 94 since it enables the body of the poker to be held horizontal while the top'extends downwardly toward the recess or pit.

No special operating mechanism is required for the doors 50 since those doors are in register with and are operated by the plunger 92. The support 88 and plate 90 will successively engage and raise the inner edges of doors 50 as the plunger, 92 moves upwardly, and this engagement will open the doors 50. Those doors will remain open as the plunger moves upwardly; merelyv resting against the sides of the plunger 92. When the plunger 92 moves down into lowered position, gravity will cause the doors 50 to close.'

'A modified form of transverse support is shown in Figs. 6 and 7; andthat support has two spaced bars 102 and 104. These bars are directly secured to a supporting plate 106 which can be bolted to a plunger that is vertically movable in acylinder. The actuator carried by the bars 102 and 104 is slotted, and it permits the chock 108 to move toward anden'gage the plunger; an inward extension of that chock being engageable with the plate I ill below and transverse projections 113 above those bars This arrangement secures the chocks 108 to the transverse. support and givesthem considerable strength. Whereas two preferred embodiments of the present invention have been shown and described it should be obvious to. those skilled in the art that various changes may be made. in the. form of: the invention without. affecting the scope thereof.

What I claim is:

- 1:. A lifting device for automotive vehicles that comprises a plunger which can be elevated and lowered, a support disposed transversely of said plunger, said support being a straight bar, chocks that are carried by said support but are adjustable along the length of said support, said chocks having vehicle-engaging portions that are eccentric of the support-engaging portions of said chocks, and are transverse of said support, said chocks having slots therein adjacent the support-engaging portions thereof, a pit in the floor of the structure in which said lifting device is to be operated, cover plates adjacent said pit, hinges that have portions fixedrelative to said pit and have other portions secured to and rotatable with said cover plates, said hinges permitting rotation of said cover plates into and out of closed position, and horizontally-extending slots in said cover plates, said chocks being taller than said cover plates are wide whereby the tops of said chocks can project above the upper edges of said cover plates when said cover plates are open and when said support is at the level of said slots in said cover plates, said slots in said cover plates and said slots in said chocks being registerablc to receive a poker, said chocks being dimensioned to engage and lift said cover plates when said lifting device starts to move upwardly from the lowered position.

2. A lifting device for automotive vehicles that comprises a plunger which can be elevated and lowered, a support disposed transversely of said plunger, chocks that are carried by said support but are adjustable along the length of said support, a pit in the floor of the structure in which said lifting device is to be operated, cover plates adjacent said pit, said cover plates normally lying in the path of movement of said chocks, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said cover plates,

said hinges permitting rotation of said, cover plates into said cover plates being openable by said linkage but also being openable manually, said linkage responding to said actuator to open said cover plates when said lifting element moves downwardly and responding to said support.

to hold said cover plates open for an additional period:

of time, said. linkage being below the level of said cover plates whenever said cover plates are, in closed position, said actuator being spaced from said portionv of said linkage a distance less than said chocks are spaced from. said cover plates whenever said. plunger is; in elevatedposition whereby said actuator can engage said. portion of said linkage and cause movement of said cover-plates. before said chocks reach. said cover plates during lowering of; said plunger, said portion of saidlinkage; being so disposed relative to said cover plates that said chocks will be in position between said cover plates before said actuator moves downwardly out of engagement with said portion. of said linkage, said chocks holding said cover plates open until said chocks. are within said pit and thereafter permitting said cover plates to close. r

3. In a lifting device. the improvement which comprises a verticallyreciprocable plunger; a. support disposed trans vetsely of said plunger, a. pit, cover platesv adjacentsaidf 8 pit, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said 'cover plates, saidhinges permitting rotation of said cover plates into and'out of closed position, a mechanical linkage of levers, said mechanical linkage having the major portion thereof disposed below and in register with said cover plates, a spring biasing said linkage to retracted position to permit said cover plates to close, said linkage being. disposed intermediate said cover plates and said support whenever said support is in lowered position, said cover plates being operable independently of said linkage and of each other.

a 4. In a lifting device'theimprovement that comprises a vertically reciprocable-plunger, a support disposed transversely of said plunger, a pit in the floor of the structure in which said lifting device is to be operated, cover plates adjacent said pit, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said cover plates, said hinges permitting rotation of said cover plates into and out. of closed position, cam plates that are on said cover plates, a mechanical linkage of levers that has actuating pins disposed adjacent said cam plates on said cover plates and that has bearingsurfaces movable to move said pins and open said cover plates, said linkage being disposed intermediate said cover plates and said support whenever-said support is in lowered position, a spring biasing said linkage to retracted position to permit said cover plates to close, and a frame of unitary character that supports said cover plates, hinges, linkage, and spring and is bodily insertable into said pit, a portion of said frame being registerable with and securable in fixed relaposed transversely of said lifting element, chocks that are carried by said support, a pit in the floor of the structure in which sai'dlifti'ng device is to be operated, cover plates adjacent said pit, said cover plates being spaced apart longitudinally. of said support, hinges that have portions fixed relative to said pit and'have other portions securedto. and rotatable with said cover plates, said hinges permitting'rotation of said cover plates into and out of closed position, a mechanical linkage of levers, cam plates on said cover plates, said linkage having actuating pins disposed adjacent the cam plates on said cover plates and having. bearing surfaces actuable to move said pins and open said cover plates, said pins being spaced apart but being connected for conjoint movement by a shaft, and an actuator that is movable with said lifting element and is in register with said bearing, surfaces of said linkage and is adapted to move them, said. actuator being spaced from said bearing surfaces and said chocks being disposed below saidv cover plates whenever said plunger is in lowered position, said actuator being spacedv from said bearing surfaces a distance which is. greater than the distance between said chocks and said cover plates whenever said plunger is in lowered position, whereby said chocks engage said cover plates and start to open them before said actuator engages said bearing surfaces during upward movement of said lifting. element.

.6, In a lifting. device for automotive vehicles, the improvement that comprises a plunger which can be elevated and lowered, a support disposed transversely of said plunger, said support having twov parallel, spaced portions, chocks thatv engage and are carried by both parallel spaced portions of said support, said chocks and said support being movable with said plunger, a pit in the floor of the structure in which said lifting device is to be operated, cover plates that are adjacent said pit and normally are disposed in the path of movement of said..chocks, hinges that have portions fixed relative to said pitan'd have other portions secured to and rotatable said cover plates into and out of closed position and into and out of the path of movement of said checks, a mechanical linkage of levers to operate said cover plates, said linkage being disposed intermediate 'said cover plates and said support whenever said support is in -lowered position, and an actuator movable with said plunger, said linkage having a portion thereof in the path of movement of said actuator that responds to move ment of said actuator to cause said linkage to operate said cover plates, said portion of said linkage beingbelow the level of said cover plates whenever said cover plates are in closed position, said chocks being adapted,

when passing between said. cover plates, to hold said cover plates apart, said actuator being spaced from said linkage a distance which is greater than the distance between said cover plates and said chocks whenever said plunger is in lowered position, whereby said chocks engage said cover plates and start to open them before said actuator engages said linkage during upward movement of said plunger.

7. In a lifting device the improvement that comprises a vertically reciprocable lifting element which can rotate as it moves vertically, a support disposed transversely of said lifting element, a pit in the floor of the structure in which said lifting device is to be operated, cover plates adjacent said pit, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said 'cover plates, said hinges permitting rotation of said cover plates into and out of closed position, a mechanical linkage of levers that has bearing surfaces which are actuable to open said cover plates, an actuator that is movable with said lifting element, and a frame that supports said cover plates, hinges and linkage, said frame comprising a plurality of elongated bars, said bearing surfaces of said linkage normally lying in the normal path of movement of said actuator, some of said elongated bars having guiding surfaces thereon that are spaced outwardly of said path of movement of said actuator but that can be engaged by said actuator when said lifting element rotates, said actuator being adapted to engage said bearing surfaces and move them and to engage said guiding surfaces to correct any misalignment of said transversely extending support due to rotation of said lifting element whenever that support enters said pit.

8. In a lifting device the improvement that comprises a vertically reciprocable lifting element, a support disposed transversely of said lifting element, a pit in the floor of the structure in which said lifting device is to be operated, cover plates adjacent said pit, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said cover plates, said hinges permitting rotation of said cover plates into and out of closed position, a mechanical linkage of levers to open said cover plates, spaced supports for said linkage of levers, and an actuator that is movable with said transversely extending support, said actuator being selectively engageable with and separable from said supports, said supports being spaced on opposite sides of the path of movement of said actuator and interacting with said actuator to center and guide said actuator and said support, said linkage having an element that is movable relative to said supports and is movable into and out of said path of movement of said actuator and is movable to actuate said linkage and move said cover plates, said element being disposed above the level of said support whenever said lifting device is in lowered position and being disposed below the level of said support whenever said lifting device is in raised position, whereby movement of said support and actuator force movement of said element.

9. In a lifting device which has a vertically reciprocable lifting element, a support disposed transversely 10 of said lifting elemenhra pit'tlrat isin the floor of the structurein which said lifting device is to be" operated and that accommodates said support, coveraplates adjacent said pit, hinges that have portions fixed relative to said pit and have otherportions secured to and rotatable with said cover plates, said hinges permitting rotation of said cover plates into and out of ,closed position, an actuator that moves with said support, bearing surfaces that selectively'receive and guide said actuator and thereby guide said support into alignment with said pit, said actuator moving out of engagement with said bearing sur: faces when said lifting element moves to elevated position, whereby said support can become askew of said pit when said lifting element is in elevated position, and a lost-motion linkage that moves the confronting edges of said cover plates apart a predetermined distance to define an open area whenever said lifting element is lowj ered, the improvement which comprises chocks that are mounted on said support and that have narrow support: engaging bottom portions, that have wide vehicle-en gaging top portions which are at right angles to said cover plates and to said hinges, and that have inclined sides that extend downwardly and inwardly from said vehicle-engaging top portions to said support-engaging bottom portions, said vehicle-engaging top portions of said chocks being wide enough to project beyond said open area defined by said edges of said cover plates and to engage said edges of said cover plates whenever said support is askew, said inclined edges being engageable with said edges of said cover plates and coacting with the lost motion of said linkage to move said cover plates apart an even greater distance and thereby provide an even greater open area whenever said support is askew relative tosaid pit, whereby said lifting element can move fully into said pit.

10. In a lifting device which has a vertically reciprocable lifting element, a support disposed transversely of said lifting element, a pit that is in the floor of the structure in which said lifting device is to be operated and that accommodates said support, cover plates adjacent said pit, hinges that have portions fixed relative to said pit and have other portions secured to and rotatable with said cover plates, said hinges permitting rotation of said cover plates into and out of closed position, an actuator that moves with said support, bearing surfaces that selectively receive and guide said actuator and thereby guide said support into alignment with said pit, said actuator moving out of engagement with said bearing surfaces when said lifting element moves to elevated position, whereby said support can become askew of said pit when said lifting element is in elevated position, and a lost-motion linkage that moves the confronting edges of said cover plates apart a predetermined distance to define an open area whenever said lifting element is lowered, the improvement which comprises chocks that are mounted on said support and that have narrow supportengaging bottom portions, that have wide vehicle-err gaging top portions which are at right angles to said cover plates and to said hinges, and that have inclined sides that extend downwardly and inwardly from said vehicle-engaging top portions to said support-engaging bottom portions, said vehicle-engaging top portions of said chocks being wide enough to project beyond said open area defined by said edges of said cover plates and to engage said edges of said cover plates whenever said support is askew, said inclined edges being engageable with said edges of said cover plates and coacting with the lost motion of said linkage to move said cover plates apart an even greater distance and thereby provide an even greater open area whenever said support is askew relative to said pit, whereby said lifting element can move fully into said pit, said support being narrow, said vehicle-engaging top portions of said chocks being several times wider than said support or said support-engaging bottom portions, said vehicle-engaging top 11 portions engaging said cover plates. and moving them to open position whenv said-1iftinge1ement moves upwardlyinsaidpit.

References- Cited in the of this pzitent UNITED STATES PATENTS 75,220 Thompso n Mar. 3 1868 530,776 Houser et a1. Dec. 11, 1894 548,606 Coe et a1. Oct. 25, 1895 Leake Oct; 13, 1925 Mulhollen Oct. 2, 1934 Snider Nov; 11, 1941 Frey Ian. 11, 1949' Thompson Mar. 15, 1949 Smith; May 23, 1950- Smith Oct. 3, 1950 Grushon Mar. 11, 1952 Webster et a] Mar. 11, 1952 

